Light sources that increase object chroma when dimmed

ABSTRACT

A method of increasing the color gamut of a multi-emitter light emitting device when dimming includes the steps of independently driving each emitter in the device, and increasing the lumen output of at least one emitter while simultaneously decreasing the lumen output of at least one other emitter, such that total color gamut increases while total lumen output of the light emitting device decreases. A light emitting device is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/489,472, filed Aug. 28, 2019, which is a '371 US National StageApplication of PCT/US18/18297, filed Feb. 15, 2018, which claimspriority to U.S. Provisional Patent Application No. 62/466,035, filedMar. 2, 2017, and U.S. Provisional Patent Application No. 62/608,590,filed Dec. 21, 2017, all of which are incorporated herein by referencein their entireties.

BACKGROUND OF THE INVENTION

When conventional light sources are dimmed, color perceptions of theobjects being illuminated by the light source become muted (e.g. duller,less saturated, less vivid, and less vibrant). This phenomenon of humanvision is known as the Hunt Effect, where at low light levels, objectsessentially appear less colorful than at high light levels. For manyapplications, such as residential lighting, museum lighting, theaterlighting, hospitality lighting, and any other application where colorperceptions and dimming are important components of the lightingsolution, it would be beneficial to compensate for the reducedsensitivity to color as the light source is dimmed.

There are numerous recently introduced LED products that feature a“dim-to-warm” technology. Filament lamps also become warmer when theydim. With “dim-to-warm” LED products, a light source featuring multipleLEDs is independently adjusted so that the correlated color temperature(CCT) of the light source becomes warmer during dimming. However, thereis no physiological reason that dim-to-warm should be a preferable orattractive lighting modality to humans. There is, however aphysiological reason that “dim-to-vibrant” should be preferable anddesirable, namely for overcoming the Hunt Effect.

Thus, what is needed in the art is a device, system and method forcounteracting the Hunt Effect and increasing object chroma when thelight source is dimmed.

SUMMARY OF THE INVENTION

In one embodiment, a method of increasing the color gamut of amulti-emitter light emitting device when dimming, includes the steps ofindependently driving each emitter in the device; and increasing thelumen output of at least one emitter while simultaneously decreasing thelumen output of at least one other emitter, such that total color gamutincreases while total lumen output of the light emitting devicedecreases. In one embodiment, the multiple LED emitters include at least7 LED emitters. In one embodiment, the at least 7 LED emitters include ared emitter, an amber emitter, a lime emitter, a green emitter, a cyanemitter, a blue emitter and an indigo emitter. In one embodiment, theplurality of LED emitters includes at least 4 LED emitters. In oneembodiment, the at least 4 LED emitters include a red emitter, a greenemitter, a royal blue (indigo) emitter, and a white emitter. In oneembodiment, the plurality of LED emitters includes at least 5 LEDemitters. In one embodiment, the at least 5 LED emitters include a redemitter, a lime emitter, a green emitter, a cyan emitter, and a royalblue (indigo) emitter.

In one embodiment, the method includes the step of linearly decreasingthe IES TM-30-15 fidelity index (Rf) as lumen output decreases. In oneembodiment, the method includes the step of linearly decreasing the IESTM-30-15 fidelity index (Rf) from about 96 at full output to about 48 atminimum dimmed level. In one embodiment, the method includes the step oflinearly increasing the IES TM-30-15 gamut index (Rg) as lumen outputdecreases. In one embodiment, the method includes the step of linearlyincreasing the IES TM-30-15 gamut index (Rg) from about 101 at fulloutput to about 140 at minimum dimmed level. In one embodiment, themethod includes the step of linearly decreasing Duv as lumen outputdecreases. In one embodiment, the method includes the step of linearlydecreasing Duv from about 0.0 at full output to about −0.03 at minimumdimmed level. In one embodiment, the method includes the step oflinearly increasing the IES TM-30-15 chroma shift in hue bin one(Rcs,h1) as lumen output decreases. In one embodiment, the methodincludes the step of linearly increasing the IES TM-30-15 chroma shiftin hue bin one (Rcs,h1) from about −0.1% at full output to about +35.4%at minimum dimmed level. In one embodiment, the method includes the stepof maintaining a constant correlated color temperature as lumen outputdecreases. In one embodiment, the light emitting device is a luminaire.In one embodiment, the light emitting device is a lamp with anintegrated base that can screw into an existing light socket or insertinto a pin-base.

In one embodiment, a light emitting device includes at least 2 LEDemitters, at least one internal controller, multiple driver circuitsconfigured to independently drive the plurality of LED emitters via theat least one internal controller, and programming logic configured toincrease the lumen output of at least one emitter while simultaneouslydecreasing the lumen output of at least one other emitter, such thattotal color gamut increases while total lumen output of the lightemitting device decreases. In one embodiment, each of the LED emittersis configured to emit a different color. In one embodiment, the at least2 LED emitters are selected from a group including a red emitter, a limeemitter, an amber emitter, a green emitter, a cyan emitter, a blueemitter, an indigo emitter, and a white emitter. In one embodiment, thelight emitting device is further configured to linearly decrease the IESTM-30-15 fidelity index (Rf) as lumen output decreases. In oneembodiment, the light emitting device is further configured to linearlydecrease the IES TM-30-15 fidelity index (Rf) from about 96 at fulloutput to about 48 at minimum dimmed level. In one embodiment, the lightemitting device is further configured to linearly increase the IESTM-30-15 gamut index (Rg) as lumen output decreases. In one embodiment,the light emitting device is further configured to linearly increase theIES TM-30-15 gamut index (Rg) from about 101 at full output to about 140at minimum dimmed level. In one embodiment, the light emitting device isfurther configured to increase the IES TM-30-15 gamut index (Rg) to atleast 120 at a 50% dimmed level. In one embodiment, the light emittingdevice is further configured to linearly decrease Duv as lumen outputdecreases. In one embodiment, the light emitting device is furtherconfigured to linearly decrease Duv from about 0.0 at full output toabout −0.03 at minimum dimmed level. In one embodiment, the lightemitting device is further configured to linearly increase the IESTM-30-15 chroma shift in hue bin one (Rcs,h1) as lumen output decreases.In one embodiment, the light emitting device is further configured tolinearly increase the IES TM-30-15 chroma shift in hue bin one (Rcs,h1)from about −0.1% at full output to about +35.4% at minimum dimmed level.In one embodiment, the light emitting device is further configured tomaintain a constant correlated color temperature as lumen outputdecreases. In one embodiment, each of the multiple LED emitterscomprises an LED die. In one embodiment, the multiple LED emitters arearranged in a single LED package. In one embodiment, the light emittingdevice is a luminaire. In one embodiment, the light emitting devicefurther comprises an external controller interface communicativelyconnected to an external controller and the internal controller.

In another aspect, a light emitting device comprises at least 2 LEDemitters and a plurality of driver circuits configured to independentlydrive the plurality of LED emitters, wherein the light emitting deviceemits light at a first fixed output level, the output level having alower total lumen output and a higher total color gamut than would beemitted if all the LED emitters were driven equally. In one embodiment,the light emitting device is also configured to emit light at a secondfixed output level, the second fixed output level having a lower totallumen output and a higher total color gamut than the first fixed outputlevel. In one embodiment, the light emitting device is configured toemit light at an ordered set of fixed output levels, and each subsequentfixed output level in the set has a lower total lumen output and ahigher total color gamut than all previous fixed output levels in theset.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The foregoing purposes and features, as well as other purposes andfeatures, will become apparent with reference to the description andaccompanying figures below, which are included to provide anunderstanding of the invention and constitute a part of thespecification, in which like numerals represent like elements, and inwhich:

FIG. 1 is a system diagram of a light emitting device according to oneembodiment.

FIG. 2A is a diagram of a 7-LED array according to one embodiment, and

FIG. 2B is an illustration of the light emitting device in a roomenvironment.

FIG. 3 is a diagram of a 9-LED array according to one embodiment.

FIG. 4A is a diagram of a 36-LED array according to one embodiment.

FIG. 4B is a diagram of a 22-LED array according to one embodiment.

FIG. 5A is a linear graph of peak wavelengths of seven emitters used inone embodiment of the invention.

FIG. 5B is a graph of relative spectral power distributions of sevenemitters used in one embodiment of the invention.

FIG. 6A is a table showing the fractional (i.e. relative) percentages ofeach of the seven LED channels used to create systematic variations incolor characteristics.

FIG. 6B is a table showing relative DMX values associated with thefractional values given in the table of 6A. FIG. 6C is a table and FIG.6D is a graph showing systematic changes in Rf, Rg, CCT, Duv, and Rcs,h1from full output to the minimum dimmed level in 10% increments.

FIGS. 7A-7K show TM-30-15 Color Vector Graphics (CVGs) [top] andassociated Spectral Power Distributions (SPDs) [bottom] for dimming fromfull output to minimum dim level in increments of 10 percent.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a more clear comprehension of the present invention, whileeliminating, for the purpose of clarity, many other elements found insystems and methods of increasing object chroma when dimming a lightsource. Those of ordinary skill in the art may recognize that otherelements and/or steps are desirable and/or required in implementing thepresent invention. However, because such elements and steps are wellknown in the art, and because they do not facilitate a betterunderstanding of the present invention, a discussion of such elementsand steps is not provided herein. The disclosure herein is directed toall such variations and modifications to such elements and methods knownto those skilled in the art.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are described.

As used herein, each of the following terms has the meaning associatedwith it in this section.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

“About” as used herein when referring to a measurable value such as anamount, a temporal duration, and the like, is meant to encompassvariations of ±20%, ±10%, ±5%, ±1%, and ±0.1% from the specified value,as such variations are appropriate.

Ranges: throughout this disclosure, various aspects of the invention canbe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Where appropriate, the description of a range should beconsidered to have specifically disclosed all the possible subranges aswell as individual numerical values within that range. For example,description of a range such as from 1 to 6 should be considered to havespecifically disclosed subranges such as from 1 to 3, from 1 to 4, from1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well asindividual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5,5.3, and 6. This applies regardless of the breadth of the range.

Referring now in detail to the drawings, in which like referencenumerals indicate like parts or elements throughout the several views,in various embodiments, presented herein are light sources that increaseobject chroma when dimmed.

With reference now to FIG. 1 , an exemplary light emitting device 40 isshown according to one embodiment. The light emitting device 40 includesmultiple LED emitters 1, 2, 3, 4, 5, 6, 7 that are each respectivelyconnected to a driver circuit 21, 22, 23, 24, 25, 26, 27. Each drivercircuit 21, 22, 23, 24, 25, 26, 27 is connected to an internalcontroller 30 that is configured to drive each respective LED emitter 1,2, 3, 4, 5, 6, 7 independently. The internal controller 30 individuallymanipulates power to each LED 1, 2, 3, 4, 5, 6, 7 as the light emittingdevice 40 transitions between full output and minimum dimmed levels. Itshould be appreciated that there is no limitation to the exact number ofemitters, for example, the device might include two or more emitters, ormight include two or more emitters of at least two different colors oflight. The device can also include multiple emitters with groups of twoor more emitters emitting the same color of light.

In some embodiments, the device comprises one or more phosphor-convertedLEDs (PC-LEDs). A PC-LED is known in the art as an LED emitter having apeak emission wavelength and also including one or more phosphors,wherein the one or more phosphors converts some of the light emitted toa longer wavelength. In some embodiments, the combination of emittersand phosphors is capable of producing a broad spectral emission with ahigh color-fidelity score. In one embodiment, the combination ofemitters and phosphors is capable of creating a spectral emission withan IES TM-30-15 Rf fidelity score greater than 90. In one embodiment,the invention comprises one blue emitter and two narrow-emittingphosphors, one in the green range (with a peak wavelength of about 530nm) and one in the red range (with a peak wavelength of about 630 nm).

The internal controller 30 can be a hardwired circuit that automaticallyadjusts power driven to each LED emitter 1, 2, 3, 4, 5, 6, 7 at variouslevels of lumen output. The internal controller 30 can also be a digitalcomponent including a chip that is programmable to control how power isdriven individually to each LED emitter 1, 2, 3, 4, 5, 6, 7 at variouslevels of lumen output. Thus, the internal controller can includecomputer logic to individually manipulate the output of the emitters.The logic can operate on a computer platform, such as a local or remoteexecutable software platform, or as a hosted Internet or network programor portal. Any computing device as would be understood by those skilledin the art may be used with the system to drive emitter signals,including desktop or mobile devices, laptops, desktops, tablets,smartphones or other wireless digital/cellular phones, or other devicesas would be understood by those skilled in the art. The light emittingdevice 40 is configured to independently drive power to the multiple LEDemitters to increase gamut as overall lumen output of the devicedecreases during the process of dimming.

In some embodiments, the light emitting device 40 further includes atleast one external controller interface, configured to communicate withan external controller. Examples of external controllers for use withthe external controller interface include, but are not limited to,commercially-available controllers that are already in widespread use.For example, an external controller interface of the present inventionmight connect to a 0-10V wall-box dimmer, a DMX512 controller, a DALIcontroller, a wireless lighting controller, a smart home controller, anambient light sensor, a daylight photocell sensor, or a time clock. Inthese embodiments, the external controller interface serves as a bridgebetween the internal controller, which sets the relative intensities ofthe various LED emitters of the device, and the external controller,which in some embodiments includes a human interface such as a switch, adimmer switch, or voice control.

In one embodiment, each of the LED emitters 1, 2, 3, 4, 5, 6, 7 isconfigured to emit a different color, however, certain embodiments mayinclude one or more sets of LED emitters that are the same color. In oneembodiment, at least 4 LED emitters emit different colors, while inanother embodiment, at least 7 LED emitters emit different colors. Withreference now to FIG. 2A, in an embodiment where at least 7 LED emittersemit different colors, an LED array is shown where colors and peakwavelengths include a red emitter (630 nm) 1, an amber emitter (590 nm)2, a lime emitter (568 nm) 3, a green emitter (530 nm) 4, a cyan emitter(500 nm) 5, a blue emitter (460 nm) 6 and a royal blue (indigo) emitter(445 nm) 7. The emitters can be for example part of an LED packagecontaining the seven LED array. As would be understood by one skilled inthe art, the wavelengths listed above are only one example of a possiblecombination of emitters and are not meant to be exclusive. In someembodiments, for example, the red emitter may have a peak wavelength of640 nm. In other embodiments, the 7 emitters may include a white emitterwith multiple peak wavelengths. The wattage or power supplied to eachemitter is independently controlled by a digital controller or a controlcircuit as described above. For illustrative purposes, the lightemitting device 40 of FIG. 2A is shown in an environment depicted inFIG. 2B as an overhead room light 40 illuminating an object 14 that isbeing observed by a person 12.

In certain embodiments, one or more LED packages are configured on aprinted circuit board or substrate. A single internal controller orcontrol circuit can be used to control multiple LED arrays, for exampleby using a common driver circuit to control the same colored LEDs foundin different arrays. The emitters can be any of the various types knownin the art, such as for example emitters known by the trade name ofLuxeon Rebel (Lumileds Holding B.V.). In certain embodiments, theemitters include an organic material and are OLED emitters. In certainembodiments, the one or more internal controllers and the one or moreLED packages are disposed on the same substrate. In certain embodiments,the emitters are configured as a liquid crystal on silicon (LCoS)lighting device. In certain embodiments, the emitters are laser diodes.In certain embodiments, the one or more LED packages are PC-LEDs.

The physical arrangement of emitters within the array can take variousforms. Arrangements can for example be symmetrical or asymmetrical. Withreference now to FIG. 3 , a light emitting device 140 is shown havingnine LED emitters 31, 32, 33, 34, 35, 36, 37, 38, 39. In this example,the arrangement of the dies is three in-line rows and columns, versusthe offset arrangement shown in FIG. 2A. In addition, the embodimentshown in FIG. 3 includes emitters of the colors and peak wavelengths ofdeep-red (650 nm) 31, red (620 nm) 32, red-orange (610 nm) 33, amber(585 nm) 34, lime (566 nm) 35, green (520 nm) 36, cyan (490 nm) 37, blue(460 nm) 38, and violet (420 nm) 39. As with embodiments describedabove, the power driven to each die by the internal controller orcontrol circuit is independent of the others.

In one embodiment having at least four LED emitters emitting differentcolors, the LED array may include emitters with peak wavelengths of red(630 nm), lime (568 nm), green (530 nm), royal blue or indigo (445 nm),and white, having a broad phosphor converted emission. In anotherembodiment where at least five LED emitters emit different colors, theLED array may include emitters with peak wavelengths of red (630 nm),lime (568 nm), green (530 nm), cyan (500 nm), and royal blue or indigo(445 nm).

Another example of an LED array is shown in FIG. 4A. In this example,the emitters are unequal in number to balance for different lumenoutputs. The power driven to each emitter is controlled independently.In this example, the emitters include the colors red (1), amber (2),lime (3), green (4), cyan (5), blue (6), and royal blue (indigo) (7).The example of FIG. 4A comprises five red emitters, ten amber emitters,seven lime emitters, five green emitters, three cyan emitters, threeblue emitters, and three royal blue (indigo) emitters.

Another example of an LED array is shown in FIG. 4B. In this example, 22emitters are used in a substantially round configuration. The colorscorresponding to each number 1-7 in FIG. 4B are red (1), amber (2),green (3), cyan (4), blue (5), royal blue (indigo) (6), and white (7).

There are two primary advantages to this configuration. First, addingmore emitters to a package increases the maximum lumen output possibleby the package as a whole. Second, emitters of the same type but of adifferent color will often have different maximum lumen outputs, due todifferences in efficiency and in the underlying chemistry necessary toproduce light of the required spectral range. One can compensate for thevariation in efficiency by using more emitters of lower efficiency toreach the same total luminous output as fewer emitters of higherefficiency.

One example of emitter color distribution is shown in FIG. 5A. Theindividual SPDs of seven emitters are shown. In FIG. 5A, the curves arenumbered as follows, with the corresponding peak wavelengths: 1) Red(634 nm), 2) Amber (597 nm), 3) Green (525 nm), 4) Cyan (500 nm), 5)Blue (475 nm), 6) Royal Blue (Indigo) (445 nm), and 7) White (564 and436 nm). The SPDs of FIG. 5A are normalized to show the shape of eachcurve, so that the peak emission wavelength of all curves are shown atthe same level. This is not meant to indicate that all seven LED diesare emitting light at the same luminous power level.

FIG. 5B shows an alternative representation of the SPDs of the sevenemitters indicated above in the description of FIG. 5A. Each curve inFIG. 5B represents the total relative radiant watts generated by eachgroup of emitters with the peak wavelengths indicated above in thedescription of FIG. 5A, and arranged as in the set of 22 emitters shownin FIG. 4B.

By adjusting the power driven to the various emitters, systematicvariations in color characteristics are created in order to increase thegamut index of the light source (hereinafter “Rg”). The invention doesso while systematically controlling changes to the fidelity index(hereinafter “Rf”), correlated color temperature (hereinafter “CCT”),“Duv”, (which is understood in the art to be a metric that quantifiesthe distance between the chromacity of a given light source and a blackbody radiator of equal CCT), and chroma shift in hue bin 1 (hereinafter“Rcs,h1”). The systematic control of these variables counteracts theHunt effect and increases object chroma during dimming according toembodiments of the invention. Fractional (i.e. relative) percentages ofeach of the various LED channels are used to create systematicvariations in color characteristics. In one embodiment, the lightemitting device is configured to limit the decrease in the IES TM-30-15fidelity index (Rf) as lumen output decreases. In one embodiment, thelight emitting device is configured specifically to limit the decreasein the IES TM-30-15 fidelity index (Rf) from about 96 at full output toabout 48 at minimum dimmed level. In one embodiment, the light emittingdevice is configured to linearly increase the IES TM-30-15 gamut index(Rg) as lumen output decreases. In one embodiment, the light emittingdevice is configured specifically to linearly increase the IES TM-30-15gamut index (Rg) from about 101 at full output to about 140 at minimumdimmed level. In one embodiment, the light emitting device is configuredto linearly decrease Duv as lumen output decreases. In one embodiment,the light emitting device is configured specifically to linearlydecrease Duv from about 0.0 at full output to about −0.03 at minimumdimmed level. In other embodiments, the light emitting device isconfigured to hold Duv nearly or completely constant. In someembodiments, the light emitting device is configured to hold CCTapproximately or completely constant. In other embodiments, the lightemitting device is configured to change both CCT and gamut,independently or in parallel. In one embodiment, the light emittingdevice is configured to linearly increase the IES TM-30-15 chroma shiftin hue bin one (Rcs,h1) as lumen output decreases. In one embodiment,the light emitting device is configured specifically to linearlyincrease the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) fromabout −0.1% at full output to about +35.4% at minimum dimmed level. Inone embodiment, the light emitting device is configured to maintain aconstant correlated color temperature as lumen output decreases. Thesesystematic changes increase object chroma during dimming, and this isdemonstrated in the experimental examples described in further detailbelow.

The light emitting device can be any type of light emitting device knownin the art for illuminating objects or a general space. In oneembodiment, the light emitting device is a luminaire such as a lamp, ora light fixture such as overhead room lighting. In another embodiment,the light emitting device is packaged into a replacement bulb that canscrew into an existing light socket or insert into a pin-base. The LEDmodule can be incorporated into luminaires, or be a luminaire inclusiveof housing and circuitry. The light emitting device can be used invarious applications, such as residential, commercial, museum, theaterand hospitality lighting.

Advantageously, embodiments of the invention manipulate the relativeproportions of optical radiation at different wavelengths (i.e. thespectral power distribution) to alter the appearance of illuminatedobjects. At high output (100%) the color gamut of the spectral powerdistribution will be comparable to a reference illuminant, which has agamut index (e.g., IES Rg, GAI) of about 100. As the light source isdimmed, not only will lumen output decrease, but the gamut will increase(e.g., IES Rg>100).

In some embodiments, the internal controller of the present inventionmay include or be replaced by a single, fixed output configuration or aset of fixed output levels that accomplish the wider spectral emissionat a lower relative light output of the present invention. For example,in one embodiment, a light emitting device of the present invention willhave only “on” and “off” states, but while in the “on” state, the lightemitting device will have a lower total lumen output than a referenceilluminant, while also having a larger gamut (e.g., IES Rg>100). Inexemplary embodiments, an emitter in the “on” state will have a fixedoutput as shown in FIG. 7H, 7I, or 7J. Alternatively, the fixed outputstate of an emitter of the present invention may be defined by anysingle column in FIG. 6A or 6B. It is understood that the embodimentsshown in FIGS. 6A, 6B, 7H, 7I, and 7J are not meant to be limiting, andthat a fixed output embodiment of a light emitting device of the presentinvention may have any fixed output wherein the total lumen output islower than a reference illuminant (i.e. dim), but the total color gamutoutput will be higher than normal, in order to show illuminated objectsin a wider, more radiant color gamut. Embodiments of the presentinvention may alternatively have a fixed set of output levels, whereinthe output level decreases and the color gamut increases in steps ratherthan continuously.

In one embodiment, a method of generating light output from a lightemitting device includes the steps of independently driving multiple LEDemitters to increase gamut as lumen output decreases. In one embodiment,the method includes the step of limiting the decrease in the IESTM-30-15 fidelity index (Rf) as lumen output decreases. In oneembodiment, the method includes the step of limiting the decrease in theIES TM-30-15 fidelity index (Rf) from about 96 at full output to about48 at minimum dimmed level. In one embodiment, the method includes thestep of linearly increasing the IES TM-30-15 gamut index (Rg) as lumenoutput decreases. In one embodiment, the method includes the step oflinearly increasing the IES TM-30-15 gamut index (Rg) from about 101 atfull output to about 140 at minimum dimmed level. In one embodiment, themethod includes the step of linearly decreasing Duv as lumen outputdecreases. In one embodiment, the method includes the step of linearlydecreasing Duv from about 0.0 at full output to about −0.03 at minimumdimmed level. In one embodiment, the method includes the step oflinearly increasing the IES TM-30-15 chroma shift in hue bin one(Rcs,h1) as lumen output decreases. In one embodiment, the methodincludes the step of linearly increasing the IES TM-30-15 chroma shiftin hue bin one (Rcs,h1) from about −0.1% at full output to about +35.4%at minimum dimmed level. In one embodiment, the method includes the stepof maintaining a constant correlated color temperature as lumen outputdecreases.

EXPERIMENTAL EXAMPLES

The invention is now described with reference to the following Examples.These Examples are provided for the purpose of illustration only and theinvention should in no way be construed as being limited to theseExamples, but rather should be construed to encompass any and allvariations which become evident as a result of the teaching providedherein.

Without further description, it is believed that one of ordinary skillin the art can, using the preceding description and the followingillustrative examples, make and utilize the present invention andpractice the claimed methods. The following working examples therefore,specifically point out the preferred embodiments of the presentinvention, and are not to be construed as limiting in any way theremainder of the disclosure.

With reference now to FIGS. 6A and 6D, fractional (i.e. relative)percentages of each of the seven LED channels are used to createsystematic variations in color characteristics. They are adjusted forlumen output based on the array of 22 LED emitters described in FIGS. 4Band 5B. In this example CCT is held constant at 3500 K. The IES TM-30-15fidelity index (Rf) changes linearly from 96 at full output to 48 at theminimum dimmed level. The IES TM-30-15 gamut index (Rg) changes linearlyfrom 101 to 140. Duv changes linearly from 0.0 to −0.03. IES TM-30-15chroma shift in hue bin one (Rcs,h1), representing red saturation,varies linearly from −0.001 (−0.1%) to +0.354 (+35.4%). Relative DMX(digital multiplex) values associated with the fractional values givenin FIG. 6A are shown in FIG. 6B. These DMX values have been adjusted forlumen output. With reference now to the example shown in FIG. 6C,systematic changes in Rf, Rg, CCT, Duv, and Rcs,h1 are shown from fulloutput to the minimum dimmed level in 10% increments. CCT was heldconstant and luminous efficacy of radiation (LER) is shown forreference.

FIGS. 7A-7K, provide TM-30-15 Color Vector Graphics (CVGs) [top] andassociated Spectral Power Distributions (SPDs) [bottom] for dimming fromfull output to minimum dim level in increments of 10 percent. The CVGsare divided into 16 hue bins, each represented by a point andrepresenting the average of the TM-30-15 hue samples taken in thatradial section of the hue graph. The vectors represent the difference inhue and saturation of each bin between the test illuminant (dark circle)and a reference illuminator (white circle). Vectors of increasingdistance from the center represent an increase in saturation, vectorsdecreasing distance to the center represent a decrease in saturation.The component of each vector tangent to the reference illuminator circlerepresents a hue shift in that hue bin. The Rg is determined by thedifference in the area enclosed by the polygons defined by the testilluminant points and the reference illuminator points, where Rg=100represents a match with the reference illuminator.

The disclosures of each and every patent, patent application, andpublication cited herein are hereby incorporated herein by reference intheir entirety. While this invention has been disclosed with referenceto specific embodiments, it is apparent that other embodiments andvariations of this invention may be devised by others skilled in the artwithout departing from the true spirit and scope of the invention.

What is claimed is:
 1. A method of increasing the color gamut of objectsilluminated by a multi-emitter light emitting device when dimming,comprising: independently driving each emitter in the device; andincreasing the lumen output of at least one emitter while simultaneouslydecreasing the lumen output of at least one other emitter, such thattotal color gamut increases while total lumen output of the lightemitting device decreases.
 2. The method of claim 1, wherein theplurality of LED emitters includes at least 7 LED emitters.
 3. Themethod of claim 2, wherein the at least 7 LED emitters include a redemitter, a lime emitter, an amber emitter, a green emitter, a cyanemitter, a blue emitter and an indigo emitter.
 4. The method of claim 1,wherein the plurality of LED emitters includes at least 4 LED emitters.5. The method of claim 4, wherein the at least 4 LED emitters include ared emitter, a green emitter, a royal blue (indigo) emitter, and a whiteemitter.
 6. The method of claim 1, wherein the plurality of LED emittersincludes at least 5 LED emitters.
 7. The method of claim 6, wherein theat least 5 LED emitters include a red emitter, a lime emitter, a greenemitter, a cyan emitter, and a royal blue (indigo) emitter.
 8. Themethod of claim 1 further comprising: decreasing the an IES TM-30-15fidelity index (Rf) of the multi-emitter light emitting device as lumenoutput decreases.
 9. The method of claim 1 further comprising:decreasing the an IES TM-30-15 fidelity index (Rf) of the multi-emitterlight emitting device from about 96 at full output to about 48 atminimum dimmed level.
 10. The method of claim 1 further comprising:increasing the an IES TM-30-15 gamut index (Rg) of the multi-emitterlight emitting device as lumen output decreases.
 11. The method of claim1 further comprising: increasing the an IES TM-30-15 gamut index (Rg) ofthe multi-emitter light emitting device from about 101 at full output toabout 140 at minimum dimmed level.
 12. The method of claim 1 furthercomprising: decreasing a distance Duv as lumen output decreases.
 13. Themethod of claim 1 further comprising: decreasing a distance Duv fromabout 0.0 at full output to about −0.03 at minimum dimmed level.
 14. Themethod of claim 1 further comprising: increasing the an IES TM-30-15chroma shift in hue bin one (Rcs,h1) of the multi-emitter light emittingdevice as lumen output decreases.
 15. The method of claim 1 furthercomprising: increasing the an IES TM-30-15 chroma shift in hue bin one(Rcs,h1) of the multi-emitter light emitting device from about −0.1% atfull output to about +35.4% at minimum dimmed level.
 16. The method ofclaim 1 further comprising: maintaining a constant correlated colortemperature of the multi-emitter light emitting device as lumen outputdecreases.
 17. A light emitting device comprising: at least 2 LEDemitters; at least one internal controller; a plurality of drivercircuits configured to independently drive the plurality of LED emittersvia the at least one internal controller; and programming logicconfigured to increase the lumen output of at least one emitter whilesimultaneously decreasing the lumen output of at least one otheremitter, such that total color gamut of objects illuminated by the lightemitting device increases while total lumen output of the light emittingdevice decreases.
 18. The light emitting device of claim 17, whereineach of the at least 2 LED emitters are configured to emit a differentcolor.
 19. The light emitting device of claim 17, wherein the at least 2LED emitters are selected from the group consisting of a red emitter, alime emitter, an amber emitter, a green emitter, a cyan emitter, a blueemitter, an indigo emitter, and a white emitter.
 20. The light emittingdevice of claim 17, wherein the light emitting device is furtherconfigured to decrease the an IES TM-30-15 fidelity index (Rf) of thelight emitting device as lumen output decreases.
 21. The light emittingdevice of claim 20, wherein the light emitting device is furtherconfigured to decrease the IES TM-30-15 fidelity index (Rf) from about96 at full output to about 48 at minimum dimmed level.
 22. The lightemitting device of claim 17, wherein the light emitting device isfurther configured to increase the an IES TM-30-15 gamut index (Rg) ofthe light emitting device as lumen output decreases.
 23. The lightemitting device of claim 22, wherein the light emitting device isfurther configured to increase the IES TM-30-15 gamut index (Rg) fromabout 101 at full output to about 140 at minimum dimmed level.
 24. Thelight emitting device of claim 22, wherein the light emitting device isfurther configured to increase the IES TM-30-15 gamut index (Rg) to atleast 120 at a 50% dimmed level.
 25. The light emitting device of claim17, wherein the light emitting device is further configured to decreasea distance Duv of the light emitting device as lumen output decreases.26. The light emitting device of claim 25, wherein the light emittingdevice is further configured to decrease Duv from about 0.0 at fulloutput to about −0.03 at minimum dimmed level.
 27. The light emittingdevice of claim 17, wherein the light emitting device is furtherconfigured to increase the an IES TM-30-15 chroma shift in hue bin one(Rcs,h1) of the light emitting device as lumen output decreases.
 28. Thelight emitting device of claim 27, wherein the light emitting device isfurther configured to increase the IES TM-30-15 chroma shift in hue binone (Rcs,h1) from about −0.1% at full output to about +35.4% at minimumdimmed level.
 29. The light emitting device of claim 17, wherein thelight emitting device is further configured to maintain a constantcorrelated color temperature of the light emitting device as lumenoutput decreases.
 30. The light emitting device of claim 17, whereineach of the plurality of LED emitters comprises an LED die.
 31. Thelight emitting device of claim 17, wherein the plurality of LED emittersare arranged in a single LED package.
 32. The light emitting device ofclaim 17, wherein the light emitting device is a luminaire.
 33. Thelight emitting device of claim 17, further comprising an externalcontroller interface communicatively connected to an external controllerand the internal controller.
 34. A light emitting device comprising: atleast 2 LED emitters; and a plurality of driver circuits configured toindependently drive the plurality of LED emitters; wherein the lightemitting device emits light at a first fixed output level, the outputlevel having a lower total lumen output than would be emitted if all theLED emitters were driven equally; and wherein objects illuminated by thelight emitting device have a higher color gamut than if all the LEDemitters were driven equally.
 35. The light emitting device of claim 34,wherein the light emitting device is also configured to emit light at asecond fixed output level, the second fixed output level having a lowertotal lumen output and a higher total color gamut than the first fixedoutput level.
 36. The light emitting device of claim 34, wherein thelight emitting device is configured to emit light at an ordered set offixed output levels; and wherein each subsequent fixed output level inthe set has a lower total lumen output and a higher total color gamut ofobjects illuminated by the light emitting device than all previous fixedoutput levels in the set.